Heretofore wellbores have been drilled into the earth's surface to penetrate one or more geologic formations containing a liquid mineral such as crude oil for recovery at the earth's surface. The crude oil and other gas and liquids produced from below the earth's surface rise through the wellbore and pass through a device located on the earth's surface known as a wellhead. From the wellhead the mixture of liquids which may also contain one or more gases such as natural gas, carbon dioxide, and the like pass from the wellhead through a pipe to a fluid treatment and storage area where gas can be separated from liquid, oil separated from water, and the like in a conventional and well known manner.
It is often desirable to remove a small sample of the liquid or liquids passing through the wellhead to the treatment and storage facility in order to obtain a better understanding of what is being produced from the wellbore at that particular time. Usually only a small sample, for example a pint or less of liquid volume, is necessary, and that sample may necessarily be obtained from the wellhead at any time of the day and under any type of weather conditions.
It is important to be able to draw one or more such wellhead liquid samples at any time, any number of times, and under all weather or other environmental conditions while minimizing if not eliminating the chance of spillage of such liquid on or around the wellhead during the sampling procedure. This way the wellhead is maintained and operated with minimal environmental impact.
In some sampling procedures an open topped sump is employed in the ground below the location where the sample is taken so that any drippings or spills will be collected in the sump for later removal and disposal in an environmentally acceptable manner. However, open topped sumps have the disadvantage of allowing the wind and other weather to have free access to the liquids collected in the sump. For example, volatile hydrocarbons can be carried off to the atmosphere by the wind thereby leaving a weathered hydrocarbon in the sump which is more viscous and more difficult to handle and dispose of. The sump also tends to collect dirt, sand, and other debris which mixes with the liquids in the sump and makes those liquids even more difficult to remove from the sump and otherwise handle in an expeditious manner. Further, when relying just on a sump, wind blown drippings from the sampling port can still be a problem because in a high wind the drippings can be blown beyond the surface area covered by the open sump top and can collect on the wellhead itself or be blown on to the surrounding terrain, all of which is desirably avoided since numerous samples are taken over the years of life of the well.